1. Field of the Invention:
This invention relates in general to a locking device for locking two threaded tubular members together, and in particular to a locking device for pipe used in offshore oil production.
2. Description of the Prior Art:
Large diameter pipes are used in offshore oil and gas production and drilling for various purposes. Each pipe has a pin on one end and a box on the other end. The pin and box have conical threads for screwing together. Often, the pin and box will have multistart threads. This allows the members to screw together with less than one full rotation.
As these members make up with only a fraction of a turn, it is important to have some type of locking means to prevent the members from unscrewing from one another. One type of locking means consists in providing tabs in the box member that are machined so that they can be deflected inward. Slots are formed in the pin member. An impact device is used to drive one or more of the tabs into the slots to lock the members together after makeup.
While this is successful, placing the locking tabs in the box member weakens the portion of the box member from the rim to the threads. This area is subject to being damaged from handling.